1. Field of the Invention
The present invention relates to an apparatus and procedure for measuring the crosssection of a hollow space, such as a tunnel, and, in particular, to a process wherein a light plane is created and pictures are taken of its reflections off of the walls of the hollow space by a camera directed at the light plane and arranged in stationary in relation to the light plane.
2. Description of the Related Art
Procedures exist for measuring hollow spaces, particularly tunnels and tubes. However, these known procedures usually demand massive amounts of work and time, and provide only an incomplete representation of the desired profile of the tunnel. Presently, the profiles can be measured trigonometrically or photogrametrically by a light section method. For example, EP-A1 0 078 179 (European Patent) describes a procedure for photographic profile detection of a tunnel. In this procedure, a light plane is generated using a circular flash arranged in a casing and halogen lamps. The casing has an inner slit opening and an outer slit opening arranged coplanar with one another. The light emerges through these openings. The profile plane thus generated on the walls to be measured is photographed, digitalized and subsequently evaluated at a fairly great expense.
British patent GB-PS 2 094 470 describes another procedure for determining surface profiles of a tunnel. In this procedure, a light ray generated by a laser is projected on the wall to be measured by a rotating mirror or a body with regular angular surfaces. All installations and devices required for the light ray generation are set up on a cart. A camera situated such that its lens axis run parallel to the longitudinal axis of the tunnel takes pictures of the profile plane generated. The path taken by the cart is measured by means of a reference laser working together with reference openings arranged on the cart. A disadvantage of this procedure is the time-consuming adjustments required to be made on the mirror or the angular surfaces and the camera.
German patent DE-PS 946 925 describes still another arrangement for taking pictures of circularly closed inside profiles of a tunnel using a lighting device and a camera that works by the above-described light section method. The lighting device is arranged in a casing, and the punctiform light source is located in the focal point of a circular Fresnel lens. A light fog is generated through this system. The camera takes pictures of the rays of this light fog reflecting from the walls of the tunnel. The lighting device is moved within the tunnel to measure different profiles. However, this causes the profiles to have different scales, and the resulting distortions make the subsequent evaluation more difficult.
East German Patent DD-PS 263 670 also describes a device for producing light sections. The invention uses two plates arranged parallel to and at a short distance from one another, a flash apparatus to generate directed light, and a camera. In addition, a light ray directed parallel to the measuring line is used. Coming from the camera, this ray strikes a mirror provided with a blackened cross, which divides the mirror into 4 parts. When the camera is arranged axially to the light section apparatus, all of the joint faces are lightened uniformly and the flash apparatus arranged between the plates as well as the camera shutter are activated.
All of the aforementioned devices generate a strip of light which in turn generates a circular lighting profile corresponding to the width of the hollow space to be measured. However, individual profiles generated in this manner do not provide any information about the shape and size of a tunnel between the individual profiles. As is generally known, cameras take pictures of the differently created profile planes and the planes can be measured directly on the photo if the scale is known and the image plane is parallel to the profile plane. In principle, however, only individual profiles are determined with the known procedures. Determining the position of the profiles in relation to one another is complicated and time-consuming and is particularly disadvantageous because it requires long work in cramped and unhealthy environments. Furthermore, because the individual profiles must be selected on site, an optimal choice of profiles is impossible in the narrow conduits and tunnels. If the result of the profiles measured proves to be unsatisfactory, additional or different profiles can only be measured at great expense. In addition, irregularities in the shape of the axis and the shape of the conduit or tunnel between the measured profiles are not detected with the known procedures. Good three-dimensional tunnel models require many profiles for the model to be a faithful reproduction, and are, therefore, quite costly. Despite a large number of profiles, damages to the conduit are neither visually documented nor detected with the aforementioned methods.
An object of the present invention is, therefore, to avoid the above-mentioned disadvantages and to provide a procedure and apparatus that makes it possible to achieve a three-dimensional model of the tunnel or the tube, while reducing the time and complexity of the measuring procedure in the tunnel or the tube.
Another object is to provide a method and apparatus that enables pictures of the position and height of the inside space of a tunnel or the like to be continuously taken and documented so that they can be called up at any time to repeat any measurements.
Yet another object of the present invention is to create an uninterrupted digital data flow to avoid errors and accelerate the calculations.
A further object is to enable the individual cross-sections to be measured to be selected at will later, outside of the tunnel.
A still further object of the present invention is to create a model of a tube or tunnel inexpensively and using single measuring procedure.
The present invention achieves these objects by providing a light plane coplanar to a surface. The light plane defines a profile plane of the hollow space and, in addition, illuminates the hollow space extending from the profile plane towards the camera. A reference ray, preferably a laser ray, is used to determine the path of progressing measurements and to provide a reference point on the surface. The distance of the light plane from a predetermined starting point, preferably the source of the reference ray, is constantly measured by a counting device and at preselected intervals by a distance measuring apparatus. Finally, the camera takes pictures of the light plane, the reference point, a plumb bob and the counting device at the same time. In another embodiment of the present invention the camera also takes pictures of a vertical marking arranged in the area of the surface. Yet another feature of the invention is that while the pictures are being taken, the light plane is moved along the longitudinal axis of the hollow space to be measured, and the movement of the light plane along the longitudinal axis of the hollow space to be measured is interrupted at certain time intervals and the position of the light beam is measured in relation to the predetermined starting point.
The present invention also provides a device to carry out the procedure according to the present invention. This device has a light section mechanism composed of at least one plate and at least one light source directed at said plate and a camera directed at the plate. The device of the present invention is simply constructed and inexpensive to operate to measure the cross-section of a hollow space according to the procedure described in the invention.
According to the principles of the present invention, the above objects are accomplished by providing a mechanism in which the plate as well as the camera, preferably a video camera, are arranged on a cart which is movable in the axial direction of the hollow space and a bearing surface and at least one front wheel and one rear wheel. The light source, which is situated in an opening of the plate, is directed at the camera. The light source is covered in a lightproof manner on the plate surface facing away from the camera. A further light source arranged in the tunnel is provided to generate a reference ray aimed at the plate. The plate also has a plumb bob. Finally, a device for measuring the distance covered is arranged on the cart in the area of the plate. The present invention is also characterized in that the helix of the light source is arranged in the plane of a surface of the plate.
According to yet another embodiment of the present apparatus, the bearing surface is a rod structure that firmly connects the camera to the plate. In a further embodiment, the plumb bob is an electronic plumb bob, and a gauge is arranged on the side of the plate facing the camera. According to yet another embodiment, the plate is made of transparent or translucent material.
Further solutions according to the principles of the present invention are characterized in that several light sources directed at the camera are arranged in the plate, the length measuring device is a counting device arranged on the front wheel of the cart, and the cart has a separate counter wheel. The plate can also be arranged on the cart in a tiltable manner by means of a tilting device. This embodiment is particularly advantageous when obstacles protruding from the tunnel wall must be avoided.
The invention may best be understood with reference to the attached drawings, wherein an illustrative embodiment is shown.